Just a small [minute?] example, but I recall pondering a picture of Michael Emerson's childhood sweetheart as a child, ostensibly from the 70s, with a book published in the 2000's featured prominently on the bookshelf behind her.

Could just be lazy set design, but, contrary to your assertion above that red herrings were'n't the showrunners' fault, this was in a period of the show where C&C REVELED in viewers cueiing into the 'subtle' visual cues that they so meticulously planted.

Actually, I said some were by design. A good example is Walt on the milk carton. But that's also an example of an easter egg just for the fans that had nothing to do with the content of the show.

There are also several examples of mistakes in the show that the audience latched onto and insisted were clues. One example is when one of the show's crew members was caught in frame ducking behind a crate. Everyone watching thought it was some big clue - who is this person? Why are they hiding? Was that Charlotte? She had red hair, I think that was Charlotte!

But the show runners admitted it was just a film flub. A crew member was in the frame and they didn't have another take.

So, yes, some of those things are intentional. Some are just jokes for the viewers that don't amount to more than just good natured fun. And some are just mistakes.

I don't recall the exact situation you're referring to. But I'd bet my bottom dollar it was just an overlooked prop.